This disclosure relates to a method of forming and the resultant design of a large area flexible light source. More particularly, the disclosure relates to the method and design of a flexible OLED light source where small area flexible OLEDs are manufactured and integrated into a large panel.
Currently, manufacturing capabilities and material property limits constrain the size of the individual organic light emitting diode (OLED) devices to a relatively small dimension. By relatively small dimension is meant an area on the order of millimeters squared or centimeters squared, i.e, less than 100 cm2 when contrasted with a large area lighting panel greater than this and on the order of feet square meter squared. Therefore, in order to obtain a large area lighting panels, individual OLEDs need to be tiled together to form the larger product.
Another issue is that current OLED materials are sensitive to oxygen and moisture. As a result, individually encapsulated OLED devices require an edge seal of some nominal width, that is, the perimeters of individual OLED devices are hermetically sealed. When positioned or tiled together in a group to form the desired large-area lighting panels, each of the individual edge seals has an adverse impact on the total illuminated area of the panel. This is generally referred to as “fill factor” or “filling factor” where the entire area of the large area lighting panel is not light emitting, and therefore the filling factor is measured as the proportion of the surface area that is illuminated or emits light relative to the total surface area of the panel.
In prior arrangements, designers generally appear to focus on total light output of the array of individual OLED devices that are joined together, and therefore ignore or do not emphasize the non-light emitting portions of the assembly. For example, when designing large area OLED panels, a typical approach is to assemble multiple glass-substrate OLED devices that are individually hermetically sealed about each of their perimeters, and arrange the sealed OLED devices in tiled fashion on a rigid frame. This approach overlooks at least two important criteria. First, this design approach fails to minimize the non-light emitting portions of the assembly that result from the sealing material that encapsulates the individual OLED devices in the large area panel and, second, ignores the goal of flexibility (where flexibility is generally defined as the ability to conform or bend the panel, without damage, to a radius of curvature on the order of about five centimeters).
Accordingly, a need exists for a large area OLED light source, and method of forming same, and one that maximizes the fill factor and more desirably provides for a flexible panel.